Points can be transformed from one coordinate system to another
using the
TRANSFORMCOORDINATES function.
Consider, for example, how the same point has 4 different sets
of coordinates depending on the coordinate system (fixture) with
which the coordinates are expressed.
After you transform a point between coordinate systems, you
might need to access its X- or Y-coordinate separately (for
example, trying to display a coordinate of a point in an operator
view's Value element, or using it in a reconfiguration operation).
This cannot be done directly.
Although
TRANSFORMCOORDINATES can take and return a point object, you
cannot create a variable of type Point to hold the object for easy
retrieval of its coordinates (only variables of type Point array are possible).
To extract the coordinates separately, you need to place the point
in an array. Once in an array, you can use the SELECT and
the ELEMENTAT
functions together to extract the X- or Y-coordinate of the
point.
You can pass
TRANSFORMCOORDINATES a point object and then place its
resulting point object in an array. Alternatively, you can pass
TRANSFORMCOORDINATES an array containing the point, and it will
return the resulting point in a point array.
Passing the source point
as a point object
When you pass
TRANSFORMCOORDINATES a point object containing the point to
transform (for example, using the POINT
function), it returns the transformed point in a point object. To
access the individual X- and Y-coordinates of the transformed
point, you must then convert the results to a point array and use
the SELECT and
ELEMENTAT
functions.
ELEMENTAT( SELECT( [ TRANSFORMCOORDINATES(
POINT(10,25), PixelToAbsolute,
Flowcharts("MainFlowchart").Camera.Image) ], Item.X),
1)
The individual parameters of the
TRANSFORMCOORDINATES function are:
-
SourceCoordinates = POINT(10,25)
-
TransformationType = PixelToAbsolute
-
CalibratedImage =
Flowcharts("MainFlowchart").Camera.Image
The data type of the output of
TRANSFORMCOORDINATES is the same as the data type of its first
parameter, the SourceCoordinates parameter. In this case, since
SourceCoordinates is a point object, the output of the
TRANSFORMCOORDINATES function is a point object, which can then
be placed in a point array using the []
operator.
The SELECT
function takes an array and an expression, and returns an array
after applying the expression to each element of a source array. In
this case, Item.X will return the X-coordinate of the point object,
so the function outputs the X-coordinate of the point object in an
array: [10].
The ELEMENTAT
function takes an array and an index, and returns the element at
that index. In this case, it returns the numeric value 10.
Passing the source point
in a point array
Since the
TRANSFORMCOORDINATES function supports multiple data types, an
equivalent approach is to use POINTARRAY
to produce a point array containing the coordinates, and pass it to
the
TRANSFORMCOORDINATES function. This function will then return
the transformed coordinates in a point array. You can then use the
SELECT and
ELEMENTAT
functions on this array.
The following example does this and returns the X-coordinate, in
the absolute coordinate system, of the top-left corner of a
region.
ELEMENTAT( SELECT( TRANSFORMCOORDINATES(
POINTARRAY([IntensityChecker.TestRegion.TopLeftX],
[ItensityChecker.TestRegion.TopLeftY]), RelativeToAbsolute,
IntensityChecker.TestRegion.CoordinateSystem), Item.X),
1)
The individual paramters of the
TRANSFORMCOORDINATES function are:
-
SourceCoordinates =
POINTARRAY([IntensityChecker.TestRegion.TopLeftX],
[ItensityChecker.TestRegion.TopLeftY])
-
TransformationType = RelativeToAbsolute
-
CalibratedImage =
IntensityChecker.TestRegion.CoordinateSystem
Since the output data type of
TRANSFORMCOORDINATES is already a point array, the []
operator is not needed to pass the result to the SELECT
function.
In this case, the SELECT and
ELEMENTAT
functions perform the same roles as in the example in the
Passing the source point as a point object subsection of this
section.
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